A Resource Reservation Protocol-Traffic Engineering (RSVP-TE), as a supplement protocol to a Resource Reservation Protocol (RSVP), is used to set up a Label Switched Path (LSP) for a Multi-Protocol Label Switching (MPLS) network.
The LSP that is set up by using RSVP-TE is capable of reserving resources, so that the services transmitted on the LSP are ensured. FIG. 1 is a schematic diagram of a setup of an LSP by using RSVP-TE. As shown in FIG. 1, two messages (a Path message and a Reserve (Resv) message) are required to set up an LSP by using RSVP-TE. A process of setting up an LSP may be briefly described as follows:
(1) An ingress node 1 generates a Path message, where the Path message may carry constraint information of setting up the LSP, and sends the Path message to an egress node 4.
(2) After receiving the Path message, the egress node 4 generates a Resv message, and returns the Resv message to the ingress node 1, and the Resv message is used to distribute labels and reserve resources on intermediate nodes 3 and 2 of the LSP.
(3) The ingress node 1 receives the Resv message, and the LSP is set up successfully.
Currently, an ACH may be used on a Pseudo Wire (PW) in an MPLS network to transmit connectivity detection information and connectivity verification information. In this way, a node that supports an MPLS-Transport Profile (TP) feature in the network may be discovered, and therefore the network is used, managed, and maintained more efficiently.
If the ACH is applied to the LSP, special packets, such as Operation, Administration and Maintenance (OAM) packets, Management Communication Channel (MCC) packets, Signaling Communication Channel (SCC) packets, and some Automatic Protection Switching (APS) packets, can be transmitted on the ACH. In this way, network management is unified, and operation is simplified. However, a prerequisite to transmitting special packets on the ACH is to negotiate an ACH capability between nodes on the LSP. If the ACH is directly used without negotiation, nodes that do not support the ACH capability may discard a received special packet or forward the packet to a user side, which leads to loss or erroneous forwarding of the packet transmitted on the ACH.
The inventor of the present invention finds that: No negotiation mechanism is available for negotiating the ACH capability between the nodes on the LSP, and therefore, a node is unaware of the ACH capability of another node and therefore unable to avoid loss or erroneous forwarding of a special packet transmitted on the ACH.